[Workbench] Child containers run on federated clusters do not show up
Child containers are determined by querying for container requests where requested_by_container_uuid matches the parent container. This does not work for federated workflows, because (a) containers run on remote clusters don't set
For (a) The arvados-cwl-runner does know which containers it is tracking. so it could explicitly update the container record with a list of child containers, similar to the runtime_status feature.